Splake

http://wildlife.state.co.us/Fishing/SpeciesID/Pages/FishID.aspx

Splake are a hybrid species of lake and brook trout with the best features of both fish. They can be difficult to distinguish as they hold characteristics from both parents. Splake have tri-colored pelvic fins like brook trout and their tails are slightly forked. Splake are found in high mountains lakes and have been used since the 1980s to thin out stunted brook trout populations. Anglers relish their large sizes (up to 18 pounds) and find success with flies, lures and bait during the summer.